The alleged assault occurred in 2013, during a Denver stopover on Taylor Swift’s Red tour.

Mueller, then a host on the top-rated radio station KYGO, had been invited to meet the star before the show. As they posed for a photo, Swift claims, “he put his hand under my dress and grabbed my bare ass”.

Recalling the night, Andrea Swift said her daughter expressed bewilderment that she had “thanked” Mueller and his then-girlfriend after the incident.

“It was just destroying her that she said that,” she testified. “As a parent it made me question why I taught her to be so polite.”

Wiping away tears, she added: “She was really shaken. She was humiliated.”

Andrea Swift, who is part of the star’s management team, said she did not report the incident to police because: “I did not want this event to define her life.”

“I did not want her to have to life through the endless memes and gifs that tabloid media and internet trolls decided to come up with – doctoring the pictures… and making her relive this awful moment over and over again.”

Asked whether she had sought witnesses, Ms Swift – who was not present at the encounter – she said she had no reason to doubt her daughter.